Improve error reporting for 'elp project-info'

Summary:
The `elp project-info` command is typically used when trying to debug project configuration.
As such, it should report any errors it finds, rather than swallowing them.

So if loading of the discovered project manifest fails, report the details before falling back to the alternative.

Reviewed By: TheGeorge

Differential Revision: D57440402

fbshipit-source-id: 6b199b89343d67a9bffaeb8c7b7a3829d74fe559

crates/elp/src/bin/build_info_cli.rs

@@ -49,11 +49,6 @@ pub(crate) fn save_build_info(args: BuildInfo, query_config: &BuckQueryConfig) -
 }
 
 pub(crate) fn save_project_info(args: ProjectInfo, query_config: &BuckQueryConfig) -> Result<()> {
-    let root = fs::canonicalize(&args.project)?;
-    let root = AbsPathBuf::assert(root);
-    let (manifest, project) =
-        load_project(&root, query_config).or_else(|_| load_fallback(&root, query_config))?;
-
     let mut writer: Box<dyn Write> = match args.to {
         Some(to) => Box::new(
             std::fs::OpenOptions::new()
@@ -64,6 +59,18 @@ pub(crate) fn save_project_info(args: ProjectInfo, query_config: &BuckQueryConfi
         ),
         None => Box::new(std::io::stdout()),
     };
+    let root = fs::canonicalize(&args.project)?;
+    let root = AbsPathBuf::assert(root);
+    let (manifest, project) = match load_project(&root, query_config) {
+        Ok(res) => res,
+        Err(err) => {
+            writer.write_all(
+                format!("could not load manifest:\n-----\n{err},\n-----\nfalling back\n")
+                    .as_bytes(),
+            )?;
+            load_fallback(&root, query_config)?
+        }
+    };
 
     if args.buck_query {
         if let ProjectBuildData::Buck(buck) = &project.project_build_data {